<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
</head>
<body>
  <div id="app">
    <h2 @click="handle">{{ message }}</h2>
  </div>

<script>
  const { createApp, reactive } = Vue

  createApp({
    setup() {
      let message = reactive('Hello vue!')
      
      const handle = () => {
        message = 'Hello Vue3'
      }

      return {
        message,
        handle
      }
    }
  }).mount('#app')
</script>
</body>
</html>